During FY13, we accomplished the following: 1) Continued analysis of P3 and P4 populations to understand the basis for stimulus-independent cell-cycle progression of P4 cells. RNA from purified P3/P4 cells were examined by microarrays and whole cell extracts were probed for cell-cycle associated proteins. Immunoprecipitation studies to identify APC-associated proteins are underway. We also utilized new DNA synthesis marker EdU to precisely define the cell cycle status of P3 and P4 populations. These studies have led to a fuller characterization of these cell populations. Additionally, we investigated whether all forms of B cell stimulation resulted in cells with similar characteristics. We found that P3/P4 equivalent cells present after LPS stimulation behaved similarly to P3/P4 cells generated after treatment with anti-CD40. That is, only P4 cells continued to divide in the absence of additional stimulation. However, both P3 and P4 populations obtained after anti-Ig treatment proliferated without additional stimulation. 2) Generated stable transfectants in BJAB cells to test the hypothesis that NF-&#954;B-dependent promoters communicate with 3UTRs to regulate mRNA lifetime of target genes. 3) Identified long intergenic non-coding RNAs that were induced in response to BCR signaling. 4) Collaborated with Ananda Roy (Tufts University Medical School) and Ali Shilatifard (Stowers Institute) to map the genome-wide H3K4me3 and H3K27me3 status in naive B cells, and cells activated via the BCR and by LPS after short-term treatment (30 min and 2h). This time-course was designed to study immediate-early gene expression in response to defined stimuli.